1. Field of the Invention
The present invention relates to an ion doping method to form source and drain, and more particularly to an ion doping method suitable to form source and drain at the deep submicron scale.
2. Description of the Related Art
With the progress of the semiconductor technology, the number of components on per unit area of a wafer increases according to Moore's law. Yet the density distribution of transistors becomes higher and higher, and the size of components becomes smaller and smaller. These will make the manufacturing process, such as the photomask pattern transfer, ion implantation and deposition, more difficult.
After the junction of a gate and source/drain becomes shallow at the deep submicron scale, the doping profile of shallow or deep ions is the main key to control the short channel effect and device driving characteristics. The conventional manufacturing process is shown in FIG. 1. First, ions are doped lightly into semiconductor substrate 12 by using gate structure 10 as a mask, and then gate spacers 14 are formed at two sides of gate structure 10. Later, dope ions heavily and anneal, by using gate structure 10 and gate spacers 14 as a mask, to form lightly doped source/drain regions 16 and heavily doped source/drain regions 18, whose concentration distribution is steep. While such manufacturing technology is adapted in the deep submicron manufacturing process, the side length of the extension regions of doped source/drain regions 16 will make the channel length shorter. At this time, electrons easily penetrate the extension regions to lead to leakage current.
Therefore, the present invention proposes an ion doping method to form source and drain to solve the above mentioned problems.